Ca2+ stores regulate ryanodine receptor Ca2+ release channels via luminal and cytosolic Ca2+ sites
Ca2+ stores regulate ryanodine receptor Ca2+ release channels via luminal and cytosolic Ca2+ sites
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DOI：
10.1529/biophysj.106.099028
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发表时间：
2007-05-10
影响因子：
3.4
通讯作者：
Laver, Derek R.
中科院分区：
文献类型：
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作者：
Laver, Derek R.
内质/肌浆网 Ca2+ 库中的游离 [Ca2+] 通过刺激 Ca2+ 释放通道来调节 Ca2+ 释放的兴奋性。储存的 Ca2+ 如何调节这些通道的激活仍然存在争议。一项提议将管腔 Ca2+ 激活归因于面向管腔的调控位点，而另一项提议则设想 Ca2+ 渗透到细胞质位点。本研究开发了一个统一的模型，用于单个心脏兰尼碱受体 (RyR(2)) 和人工脂质双层中耦合簇中的 RyR 的腔内 Ca2+ 激活。结果表明，RyR2 的管腔调节涉及与分子不同部分的 Ca2+ 传感器相关的三种作用模式；一个管腔激活位点（L位点，60μM亲和力），一个细胞质激活位点（A位点，0.9μM亲和力）和一个新的细胞质失活位点（I-2位点，1.2μM亲和力）。管腔 Ca2+ 激活 RyR 被证明是通过称为管腔触发 Ca2+ 馈通的多步骤过程发生的。 Ca2+ 与 L 位点的结合会启动短暂的开口（1-10 s(-1) 时持续 1 毫秒），允许腔内 Ca2+ 进入 A 位点，从而使开口时间延长多达 30 倍。该模型解释了广泛的数据集，协调了之前的相关观察结果，并为理解药物、RyR 相关蛋白和 RyR2 突变对一系列 Ca2+ 介导的生理和病理过程的作用奠定了基础。
The free [Ca2+] in endoplasmic/sarcoplasmic reticulum Ca2+ stores regulates excitability of Ca2+ release by stimulating the Ca2+ release channels. Just how the stored Ca2+ regulates activation of these channels is still disputed. One proposal attributes luminal Ca2+-activation to luminal facing regulatory sites, whereas another envisages Ca2+ permeation to cytoplasmic sites. This study develops a unified model for luminal Ca2+ activation for single cardiac ryanodine receptors (RyR(2)) and RyRs in coupled clusters in artificial lipid bilayers. It is shown that luminal regulation of RyR2 involves three modes of action associated with Ca2+ sensors in different parts of the molecule; a luminal activation site (L-site, 60 mu M affinity), a cytoplasmic activation site (A-site, 0.9 mu M affinity), and a novel cytoplasmic inactivation site (I-2-site, 1.2 mu M affinity). RyR activation by luminal Ca2+ is demonstrated to occur by a multistep process dubbed luminal-triggered Ca2+ feedthrough. Ca2+ binding to the L-site initiates brief openings (1 ms duration at 1-10 s(-1)) allowing luminal Ca2+ to access the A-site, producing up to 30-fold prolongation of openings. The model explains a broad data set, reconciles previous connecting observations and provides a foundation for understanding the action of pharmacological agents, RyR-associated proteins, and RyR2 mutations on a range of Ca2+-mediated physiological and pathological processes.